In the windshield wiper installations on motor vehicles in general, the wipers mounted on the ends of the oscillable arms, comprise a wiper blade, generally made of rubber, engaged with a support including a main curved rod whose ends are articulated on the middle of a pair of small bridges which, with their ends form four engagement points for a lamina which carries the rubber wiper blade.
The known structure of the back supports for the wiper blades forms, thus, an assembly including at least three arcuated elements which are coplanar, superimposed and mutually articulated and being moderately elastically deformable under the load of the oscillable arm, for the purpose of a better adaptation of the wiper blade to the glass surface which is often curved with a non constant radius.
The articulations between the ends of said main rod, provided with the connecting member for the oscillable arm, and the central portion of the secondary small bridges, assume a remarkable importance because they must allow a certain amount of a relative movement, in the longitudinal direction, to the mutually articulated elements and, in the same time, they must possibly prevent any movement of said elements in the transverse direction; said articulations must further operate without evident clearance and noise.
Another feature required for said articulations is their effectiveness even if they are constantly exposed to the atmospheric agents, mud splashes and dust.
According to the present state of the technique these articulations are generally formed by transverse pins engaging the forked ends of the main rod with respect to the central point of the secondary small bridge back. In order to minimize the noise, plastic material inserts are frequently used which, if suitably shaped, avoid the direct contact between the surfaces, facing one another, of the articulated parts, when these are made of a metal. But this expedient does not eliminate the use of the transverse pins of the articulations and the possible oxidation and jamming of these pins with respect to the crossed metal parts.